Foraminous sheet material and luminaire made therefrom



y 1950 L. c. DOANE FORAMINOUS SHEET MATERIAL AND LUMINAIRE MADETHEREFROM 2 Sheets-Sheet -1 Filed NOV. 5, 1945 LVYW INVENTOR "1J6; 4M1mam, ATTORNEYS May 9, 1950 c. DOANE FORAMINOUS SHEET MATERIAL ANDLUMINAIRE MADE THEREFROM Filed Nov. 5, 1945 2 Sheets-Sheet 2 w UV Mv/vvv INVENTOR ATTORNEYS Patented May 9, 1 950 UNITED STATES- earssr OFFICE'FORAMINOUS SHEET MATERIAL AND LUMINAIRE MADE THEREFROM Leroy C. Duane,Essex, Conn. "KpplicatioirNovember 5, 1945, Serial Ne. 626,747

1: Thisinvention relates to fcranrin'ous or perfora't'e'd sheet materialwhich will'transmit a substantial amount of light through the same andwhich is useful for illuminating devices, such as lighting fixtures orluminaries, electric signs, and similar uses. The invention also relatesto lighting devices made from the novel material.

It has heretofore been proposed to use perforated sheet metal for makinglighting fixtures and signs. While such perforated sheet metal transmitsa fair percentage of the light and is capable of producing pleasingeffectsymuch of the" light is cut oil or is lost by crossreflection inthe perforations and the sheets have the disadvantage that the outersurface thereof does not receive direct rays of light and thereforepresents a. dar'kappearance, detracting from the desired luminous effectof the entire fixture or sign. This is due to the fact that the sidewalls of the perforations are parallel and therefore do noteffectively'reflect the rays out of the fixture. Also, the outer surfaceof the imperfor'ate part of the sheet which constitutes the"greaterrpart of the area, is not directly illuminated and thereforepresents a dark appearance. It is the object of thepresen't inventionto'over'c'omethe'se defects andthis is accomplished by inclining the sidewalls of the holes orpe'rforat'ions so'tliat th'ey will reflect any raysfalling on the walls'downwardly or outwardly, theside wallspreferablybeing brought to an edge so that the 'exposed side of the sheet consistsessentially of numerous intersecting edges, there'being no'substantialflat areas presenting a dark appearance. Preferably the material used isof a reflecting nature,usually sheet metal, which may be brightlyfinished. In some instances brightly finished plastic-might be; used,but metal is usually the cheapest and most satisfactory material. Thebright inclined surfaces forming the side walls of the perforations thuswill reflect the maximum amount of light and the entire exposed face ofthe sheet will present a continuous bright appearance, without'anyshadows or dark spots. Avery brilliant and pleasing efiect is thusproduced. The novel; material of this invention isparticularly useful inconnection withilluminating devices presenting a more or less extendedarea, of illumination, such as fluorescent tubes. With such a source ofillumination the light is Well distributed back of the perforationsso-that a spotty effect is avoided and a very effective, completelyluminous fixture is produced.

y The accompanying drawings, wh chshow cer- 11 Claims. (01. am -108 2tainpreferred embodiments of the invention, are illustrative of theprinciples thereof. I

Fig. l is a perspective view of a conventional lighting fixture orlurninaire made of the improved fcraminous' material.

Fig. 2 is a diagrammatic view in longitudinal section showing a portionof a fluorescent tube and a sheet of the improved material below thesame, illustrating the paths of light rays.

Fi 3 is view showing a sheet of the material in perspective asviewedfrom the underside; and showing a portion of the fluorescent tube.

Fig. 4 is a plan view of the outside of a piece of the material.

Fig. 5 is a transverse sectional view of a sheet showing a modified formof perforation.

Fig. 6 is a transverse sectional view of a'woven wire mesh fabric havingsome of the characteristics of the perforated sheet shown in. Figs. 2and 3.

Fig. '7 is a sectional perspective view, showing the underside of amodified form of perforated sheet.

Fig. is a diagrammatic view similar to Fig. 2, showing the action ofthelight rays in connection with the conventional perforated sheet of theprior art.

Figs. 9, 10, and 11 are plan views of sheets having modified forms ofperforations. 1

Fig. 12 isa transverse sectional view of a modified form of perforatedsheet, and

Fig. 13 is a transverse sectional view of a sheet having a transparentfilling in the perforations.

Referring to the drawings in detail, andparticularly to Figs. 1, 2, and3: Fig. 1 shows a conventional form of luminaire containing a source oflight such as a plurality of fluorescent tubes. (not shown) enclosed ina casing partly or wholly made of the foraminous sheet material of thepresent invention. As illustrated, bottom, sides and ends of the casing2E! are all made of perforated material. 7

Fig. 2 shows a portion of a fluorescent tube 22 and a sheet of thematerial 24 below the same. In the form shown the sheet hasholestherethrough which are round at the top or inside as shown at 25,and the side walls 28 of which flare outwardly meeting in edges 39 atthe outside of the sheet. These edges intersect so that at the outsideof the sheet the openings are rectangular. There are thus no flatsurfaces on the outside of the sheet but only on the intersecting edges,as

clearly shown in Fig. 3.

The angle of inclination of the side walls 28 depends'upon the closenessof spacing ofthe perforations. A convenient spacing is such that theside walls when brought to an intersection so as to form the edges 30have an angle in the neighborhood of 60 degrees more or less to theplane of the sheet. The section between the perforations is thus that ofan equilateral triangle. If the holes are spaced a little farther apartthe angle would be nearer 45 degrees, and if the spacing is closer theangle would be more than 60 degrees. 60 degrees, however, is a desirableangle. With such an angle it will be seen that light passing through theperforations from an extended source of light such as a fluorescent tubewill strike the side walls as indicated by the ray in Fig. 2, and bereflected outwardly. This light will illuminate the inclined surfaces sothat they will appear bright from below the sheet. As there are noexposed surfaces in theplane of the sheet but only edges the entiresheet will appear luminous and there will be no shadows or dark spots.The form of perforations shown also permits substantial increase in theemission of light from the luminaire. This is apparent by comparing thepath of the rays in Fig. 2 with the path of the rays in the case of anordinary perforated sheet as shown in Fig. 8. The maximum emission oflight in the case of a parallel side perforation is that emitted betweenthe rays bb of maximum inclination capable of passing through theperforations, these being emitted from the length of the fluorescenttube between the lines I) and b. On the other hand with the inclinedwall perforations light is emitted between the limiting rays aa, thislight coming from the length of the tube included between lines a and a(Fig. 2). Thus it will be seen that there is a substantial increase inthe amount of illumination obtained by the use of the improved form ofsheet.

With the parallel wall perforations as shown in Fig. 8 there is muchlight absorbed in cross reflection, as shown by ray cl in that figure.

Sheets 24 are made of metal although they maybe made of other suitablematerial such as plastic capable of taking bright finish so as toprovide a reflecting surface. The perforations may be formed in anysuitable manner, as by means of a proper punch or die, or combined punchand die. The sheet may also be formed by die casting or by use of bent,stamped or extruded strips or sheets, as indicated in Fig. 7.

"The side walls of the perforations need not be plane surfaces but maybe concavely curved, as shown at All in Fig. 5. Also, the perforationsneed not be circular but may be rectangular, as shown in Fig. 9. Theedges 35 do not necessarily cross each other at right angles but may bearranged in. any suitable manner, as for instance in a diagonaldirection, as shown in Fig. 16. Furthermore they might be arranged in ahexagonal pattern, as shown in Fig. 11. I

The thickness of the sheet and size and spac ing of the perforations maybe varied to suit conditions. As a typical example, but withoutintending any limitation of the scope of the invention, a convenientthickness of sheet is about of an inch, with the holes about 3*; of aninch diameter at the inner surface of the sheet.

Another form of sheet or screen embodying some of the characteristics ofthe present invention is shown in Fig. 6. In this case the lighttransmitting sheet or screen is formed of wire mesh composed oftriangular wires t6 woven in the manner of an ordinary screen andpresenting edges 48 on the outside or side away from the source oflight. Such a wire mesh will emit a much larger percentage of light andpresent a brighter appearance than a mesh made of round wires. Theangular wire mesh will permit the passage of additional light rays in amanner clear from what has already been said.

Fig. 12 shows a form of perforated sheet in which the walls of theperforations diverge from the center of the sheet to both the upper andlower surfaces thereof. This form of perforation will permit the passageof rays in a manner similar to that indicated in Fig. 2, but permits thesheet to be made twice the thickness so that it will have increasedstrength.

In Fig. 13 a perforated sheet is shown in which the perforations arefilled with transparent material such as plastic or glass. The sheet canconveniently be made by pressing or rolling a sheet of plastic, while insoftened condition, against the bottom surface of the sheet so that theplastic will be forced into the perforations. The plastic filling theperforations is indicated at Ell. Preferably a thin layer of the plasticis permitted to extend across the under side of the sheet, so as tocover the meeting edges between the perforations, such thin layer ofplastic being indicated at 52. By providing a thin layer of plastic overthe edges, the lower surface of the sheet can be made perfectly smooth.The transparent plastic permits the rays to pass through as described inconnection with Fig. 2, but excludes dust. The outer surface of theplastic may also be given any desired ornamental formation or effect.Also the plastic may, if desired, be colored so that a luminaire madewith this sheet will emit a colored or tinted light.

While I have illustrated and described in detail certain preferred formsof my invention, it is to be understood that changes may be made thereinand the invention embodied in other structures.

I claim:

1. A luminaire comprising a source of diffused illumination of largearea with a light transmitting screen in front of the source ofillumination; said screen comprising a sheet having holes therethrough,said holes having wall portions which diverge outwardly towards the sideof the screen furthest from the source of illumination, said wallportions of adjacent holes merging to form substantially sharp edges onthe side of the screen furthest from the source of illumination, saidWall portions being of such angularity with reference to the plane ofthe sheet as to receive rays from the source of light and reflect themto the outside of the sheet.

2. A light transmitting screen for use with fluorescent tubes and thelike, comprising a wire mesh formed of woven wires of triangular crosssection, the bases of the triangles facing the inside of the screen andthe apices of the triangles facing the outside of the screen.

3. A light transmitting screen for use with fluorescent tubes and thelike, comprising a sheet of metal havin closely spaced smallperforations therein, the walls of the perforations flaring outwardlyand merging to form intersecting edges arranged in a regular patternover the outer surface of the screen, and transparent plastic materialfilling the perforations and extending in a thin layer over theintersecting edges between the perforations.

4. A light transmitting screen for use with fluorescent tubes and thelike, comprising a sheet of metal having closely spaced perforationstherein, the walls of the perforations flaring from the center ofthesheet towards the inner and outer surfaces of the sheet, and merging toform intersecting edges arranged in re ular patterns over the surfacesof the sheet.

5. A light transmitting screen for use with fluorescent tubes and thelike comprising a sheet of metal having closely spaced smallperforations therein, the walls of the perforations flaring outwardlyand merging to form intersecting edges arranged in a regular patternover the outer surface of the screen, the inner surface of the screenbeing substantially smooth throughout.

6. A luminaire adapted to hold a fluorescent tube and having a lighttransmitting screen in front of the tube position comprising a sheet ofopaque material having closely spaced, small perforations therein, thewalls of the perforations flarin outwardly and merging to formintersecting edges arranged to form a series of polygons constitutingsubstantially the entire outer surface of the screen, said flaring wallportions having light reflecting surfaces.

7. A luminaire adapted to hold a fluorescent tube and having a lighttransmitting screen in front of the tube position comprising a sheet ofopaque material having closely spaced, small perforations therein, thewalls of the perforations flaring outwardly and merging to formintersecting edges arranged to form a series of polygons constitutingsubstantially the entire outer surface of the screen, said flaring wallportions having light reflecting surfaces, the minimum diameter of theperforations being about equa to the thickness of the sheet.

8. A light transmitting screen comprising a sheet of opaque material ofuniform thickness having closely spaced, small perforations therein, theperforations bein of a minimum diameter approximately equal to thethickness of the sheet and having their centers spaced apart atdistances approximately equal to twice the thickness of the sheet, thewalls of the perforations flaring outwardly and merging to formintersecting edges, the flaring Walls of the perforations having lightreflecting surfaces.

9. A light transmitting screen comprising a sheet of opaque material ofsubstantially unlform thickness having a plurality of closely spaced,small perforations therein, the thickness of the sheet being not morethan double the minimum diameter of the perforations, said perforationsincluding flaring wall portions merging to form intersecting edges on aside of the sheet, said flaring wall portions having light reflectingsurfaces.

10. A light transmitting screen comprising a thin metal sheet ofsubstantially uniform thickness having plurality of closely spaced smallperforations therein, said perforations having wall portions flaring atangles of not more than about 60 from the plane of the sheet, saidperforations being spaced close enough together so that the edges of theflared wall pertions of adjacent perforations substantially merge, saidflared wall portions having light reflecting surfaces, Whereby, whenlight is transmitted through the screen from the back thereof, the faceof the screen presents a substantiall continuous series of flaring lightreflecting portions producing an effect of a substantially continuousluminous surface.

11. A luminaire adapted to hold a fluorescent tube having a lighttransmitting screen in front of the tube position formed as set forth inclaim 10.

LEROY C. DOANE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,236,137 Bastow Aug. '7, 19171,241,886 Rowe Oct. 2, 1917 1,309,644 Lohnes July 15, 1919 1,589,018Ludwig June 15, 1926 1,625,407 Bir Apr. 19, 1927 1,686,525 House Oct. 9,1928 2,161,957 Giese June 13, 1939 2,223,841 Biller Dec. 3, 19402,341,895 Beck Feb. 15, 1944 2,398,624 Decker Apr. 16, 1946

